A wind power generation facility including an upwind wind turbine has been developed. The upwind wind turbine is one type of horizontal axis wind turbine. At a normal time, a rotor to which a plurality of blades are attached is oriented upwind to be rotated, and electric power is generated based on a rotational force of the rotor. According to a typical upwind wind turbine, the blades are fixed to stand (hereinafter referred to as a “standing state”) such that each of coning angles of the blades becomes substantially 0°, and the blades are rotated in a substantially vertical plane (rotational plane) around a rotation axis of the rotor.
The blades are oriented upwind. Therefore, when the wind is strong, loads from the wind to the blades (hereinafter referred to as “wind loads”) increase. On this account, for example, PTL 1 discloses a technology in which: when a wind speed exceeds a threshold, the rotation of the rotor is stopped, and the postures of the blades are changed from a state where the blades are positioned in an operating plane in the standing state to a state where tip ends of the blades are tilted downwind; and with this, aspect areas (projected areas) of the blades when viewed from the upwind side are reduced while maintaining an upwind posture of the rotor, and thus, the wind loads acting on the blades when the wind is strong are reduced.
Further, for example, each of PTLs 1 and 2 proposes an upwind wind turbine including: a tilting mechanism for realizing the above operation of tilting the blades; and a driving device for driving the tilting mechanism.